BP-X: manage multiple pre-sized buffers to avoid realloc of huge single buffer

[pnorbert]

PIConGPU may use all memory so that ADIOS buffer just fits. If a realloc would happen, it could fail due to lack of memory. Still, a some memory would be available to create another buffer to store more data.

Suggestion: BP-X should manage multiple smaller buffers (we are talking about 500MB, 1GB buffers here) and let (sophisticated) user create these buffers on the fly.

[ax3l]

cc @franzpoeschel @psychocoderHPC